Winterising diesel engine when the boat is kept afloat

[sealegsjim]

My boat has a Yanmar 2GM20F diesel which is fresh water cooled with a heat exchanger and has antifreeze in the system. I thought that this would afford protection in the winter months when it is afloat in the marina. A guy from the local boatyard said that it could still freeze and it is best to drain down the system to be safe. He said he would do it for a 'reasonable fee' Is he just touting for trade or should |i be concerned? Does anyone have any ifo on the subject? I have tried the Yanmar site but it is not very helpful

 

[pvb]

Unless temperatures get unbelievably low, a boat afloat in a marina shouldn't have a problem with freezing if there's sufficient antifreeze in the cooling circuit. I'd decline his kind offer.

 

[Severnman]

Touting! Check antifreeze by all means. What will you do with your car when its really cold?

 

[Aeolus]

If your boat is in the water, then the temperature in the boat is not going to be significantly lower than the water temperature. So how cold does the water get in your marina? I'm on the south coast and the water temperature doesn't get anywhere near zero so I never worry about anything freezing. I suppose if there was an extended very cold period, then the interior of the boat would edge towards the outside air temperature, but it wouldn't happen overnight so you would have a period to do something about draining the system, or putting on the heater. If you have mains power, you could keep a greenhouse heater running all the time - I do, but that's mainly to help reduce condensation and damp.

 

[nickcred]

Mine was in all last winter (on the Thames not coastal) I put tube heater with a temp controlled theromstatic plug in the engine bay and just drained the fresh water system. All was well

 

[Dave_Seager]

My boat has a Yanmar 2GM20F diesel which is fresh water cooled with a heat exchanger and has antifreeze in the system. I thought that this would afford protection in the winter months when it is afloat in the marina. A guy from the local boatyard said that it could still freeze and it is best to drain down the system to be safe. He said he would do it for a 'reasonable fee' Is he just touting for trade or should |i be concerned? Does anyone have any ifo on the subject? I have tried the Yanmar site but it is not very helpful

Although you have antifreeze in the fresh water part of the cooling system there is still the raw water system to consider. You do not say where your boat is kept but basically, you need to consider whether the water your boat floats in is likely to freeze. Salt water will not usually freeze but your profile shows you are in the North East so I imagine it can get pretty cold up there. Obviously, the risk of freezing is higher if you are moored in fresh water.

If your boat has a domestic water system then that too can freeze.

Evein in the South East, I always drain the freshwater system and the engines' raw water systems on my boat. It does not take long to do and avoids the risk of expensive damage if the winter is severe. Equally, it does not take long to refill if you you want to use the boat during the winter.

 

[Nealo]

There's a fairly recent quite lengthy thread on this somewhere isn't there? I recall making the point that there must be hundreds if not thousands of boats on the inland waterways with raw water cooling systems that never give this any thought, even when the canals freeze up, as they did with a vengeance last year. As I understand it the accepted way of winterising a raw water system is by closing the seacock & running the engine whilst pouring anti freeze solution via the filter - until you see the coloured water come out of the exhaust. Some folk just run some fresh water through don't they. I don't think it's a good idea to try to purge the system of water completely, not sure exactly why though.

 

[Cloven]

No need to drain

This is what I do for my 2GM 20F

Antifreeze - Fresh water system - lasts from 2 to 5 years depending on the grade used. If you are not sure how long or what grade, then its time to change!!. The drain tubes are very close to the lift pump on the starboard side of the engine. There will be a small knurled knob at the top of each pipe. Open both but you will probably find that little or none comes from the top tube. You will need a container to catch the draining antifreeze. I would then flush it through with fresh water until the draining water runs clear. Note the colour of the antifreeze - it will probably be either green or blue and best to use the same type to refill as there can be an incompatibility between types. Filler is on top of the heat exchanger. Don't forget to empty & refill the antifreeze expansion reservoir.


Antifreeze - Raw water system - Once all the other jobs have been done and before you reconnect the raw water feed from the strainer to the pump, fill a bucket with antifreeze and put the inlet hose from the pump into the bucket and start the engine to draw antifreeze into the raw water cooling system. It will only take a few seconds to pump around 5 litres of antifreeze through the system. Best to have a bucket under the raw water outlet on the stern to catch the waste antifreeze.

Hope this helps

 

[Bomlo]

Alternative procedure if you have a Vetus type stainer mounted above the waterline: Close raw-water inlet, open strainer lid and fill up with antifreeze mix, start engine, refill with 5 - 10l antifreeze, stop engine. It is a two man job. Takes 3 minutes from start to finish.

Optionally: Drain raw water pump to protect impeller.

 

[Ruffles]

I now always flush with AF/inhibitor. Otherwise the salt water sits in the high rise manifold and rots it out. I'm on my third in 10 years!

 

[sealegsjim]

Thanks to everyone for their advice and I should have made it clear that the boat is kept in a marina on lake Windermere so obviously it is fresh water and could in theory freeze over. I have shore power so maybe a small low powered heater may be the answer. Anyway, thanks to you all for taking the trouble to answer my question.

 

[billiew]

Winterising engine

The only thing I would add is that I I run a hose with fresh water into the water strainer to flush out any deposits of salt etc.before the antifreeze solution.I do this with the block drain taps open,then leave them open.
Bill

 

[TheBoatman]

No need to drain

This is what I do for my 2GM 20F

Antifreeze - Fresh water system - lasts from 2 to 5 years depending on the grade used. If you are not sure how long or what grade, then its time to change!!. The drain tubes are very close to the lift pump on the starboard side of the engine. There will be a small knurled knob at the top of each pipe. Open both but you will probably find that little or none comes from the top tube. You will need a container to catch the draining antifreeze. I would then flush it through with fresh water until the draining water runs clear. Note the colour of the antifreeze - it will probably be either green or blue and best to use the same type to refill as there can be an incompatibility between types. Filler is on top of the heat exchanger. Don't forget to empty & refill the antifreeze expansion reservoir.


Antifreeze - Raw water system - Once all the other jobs have been done and before you reconnect the raw water feed from the strainer to the pump, fill a bucket with antifreeze and put the inlet hose from the pump into the bucket and start the engine to draw antifreeze into the raw water cooling system. It will only take a few seconds to pump around 5 litres of antifreeze through the system. Best to have a bucket under the raw water outlet on the stern to catch the waste antifreeze.

Hope this helps

That's exactly what I do every year on my boat and I've never had a problem.

Peter.
TheBoatman

 

[DanBurrill]

There's a fairly recent quite lengthy thread on this somewhere isn't there? I recall making the point that there must be hundreds if not thousands of boats on the inland waterways with raw water cooling systems that never give this any thought, even when the canals freeze up, as they did with a vengeance last year. As I understand it the accepted way of winterising a raw water system is by closing the seacock & running the engine whilst pouring anti freeze solution via the filter - until you see the coloured water come out of the exhaust. Some folk just run some fresh water through don't they. I don't think it's a good idea to try to purge the system of water completely, not sure exactly why though.

There aren't that many boats on the inland waterways with raw water cooling systems - the vast majority of steel narrowboats use keel cooling (via a large tank welded to the inside of the baseplate). Also, as a fair proportion of them are liveaboards, they're heated anyway in order to keep the occupants warm.

 

[idpnd]

As air temp is getting below zero, I am faced with the exact same question: Boat is to remain in water in ready to sail state - when do I have to worry about raw water part freezing? Location SE UK - Salt water

 

[TheBoatman]

My Answer

As air temp is getting below zero, I am faced with the exact same question: Boat is to remain in water in ready to sail state - when do I have to worry about raw water part freezing? Location SE UK - Salt water

You asked the question "when should you start to worry", my answer would be "when the sea starts to freeze", until then I wouldn't worry.
Most of your engine is sitting below the waterline and out of any drafts ~ so it is surrounded by water that is (say) +5 - 6 degs C, well above freezing.
You didn't say whether your engine is freshwater cooled or raw water cooled but I assume that if it's freshwater you'll have antifreeze in the system, so the only part that may freeze is the heat-exchanger and that partly drains down after you stop the engine!

If your engine is raw water cooled then providing the air temp doesn't drop below -6c for any long period I wouldn't worry.

Peter
TheBoatman.

 

[idpnd]

You didn't say whether your engine is freshwater cooled or raw water cooled but I assume that if it's freshwater you'll have antifreeze in the system, so the only part that may freeze is the heat-exchanger and that partly drains down after you stop the engine!

Thanks for the elaborate response Peter - just what I was looking for. It's a dual circuit cooling sys, antifreeze in internal bit. As you point out, I'd be most worried about the bits of seawater in the heat exchanger and raw water pump (around the impeller etc) freezing up. Since boats are kept in the water year round I guess the seawater residual temp around and the salinity stop that from happening?